This invention relates to a method and apparatus for the analysis and diagnosis of the gait of human beings and more particularly to a method and apparatus for viewing the plantar aspects of the feet while in motion, i.e., the changes in the area of contact as a patient walks for purposes of analyzing and diagnosing the natural full gait cycle of the patient.
A satisfactory system for the biomechanical gait analysis of human beings for the diagnosis and treatment of podiatric and related health problems is not presently available. Such a system may be used to diagnose and predict potential health problems, monitor treatment of existing problems, design prosthesis and orthotic devices and improve the design of footwear. Obviously such a system would provide an additional important tool to that presently available to podiatrists, orthopedists, neurologists and neurosurgeons, pediatricians, physicians specializing in physical rehabilitation and sports medicine, and to physical therapists, orthotists (those who produce specialized footwear), prosthetists (those who produce artificial body parts) among others. The equipment available and the known prior art, however, has not provided the means for studying the patient in motion and obtaining pictures of a foot's plantar aspects while in motion. As one walks the contact and noncontact surface areas of the foot change continuously. Quantifying the amount of contact area, amount of pressure exerted, the relationship of the former to the latter and all in relationship to time as each foot moves from heel strike to toe off positions during the normal gait cycle would produce information not presently available to practitioners in the arts.
One full gait cycle occurs between heel strike of one foot to heel strike by the same foot at the next step. A portion of this cycle for each foot, e.g., approximately 62% is the "stance phase" beginning with heel strike and terminating with toe off during which time the foot bears body weight. The remaining portion of the gait cycle for each foot, e.g., approximately 38% is the "swing phase" between toe off and heel strike and during which the foot is non-weight bearing and swings between steps. "Stance phase" of gait refers to the time intervening from the heel contact of the foot to the end of toe off of the same foot. "Mid stance" refers to the period from heel strike to just before heel off of the same foot. Heel off to toe off refers to the propulsive phase of gait of the single foot. During the mid stance period of one foot the other foot is in the swing phase of its gait cycle so that the weight bearing foot is alone carrying body weight. There is a phase at the end of toe off of one foot and the early heel contact of the contralateral foot when both feet bear weight. The toes bear weight during the propulsive period while they are inactive during the heel strike period and it is uncertain how significant the weight bearing of the toe is during midstance. During the swing phase the foot is carried from one step to the next. If the gait cycle is improper, the contact surface of the foot will not permit the forces acting on the foot during the various periods of the stance phase to be transferred through the various joints correctly, and this results in compensating shifts of various load bearing parts of the body, which over time produces damage to the parts thereof. For example, some spine problems can be traced to an improper gait resulting in abnormally restricted motion at certain joints so that the force of heel strike during the stance phase is not absorbed by the joints within the foot and lower extremity but are transmitted directly into the trunk of the body without proper attenuation of forces. Certain knee problems can also be traced to improper gait. Degenerative joint disease, muscle spasm and chronic low back pain are possible problems associated with faulty shock absorption due to an improper gait.
The relative positions of both feet during the gait cycle is important in determining the stage of the cycle for either foot. Watching a person walk and observing the motion and position of the foot throughout the gait cycle is extremely valuable in clinical examination and treatment.
The prior art, however, has not provided the practitioner with the tools necessary to study in detail the patient while in motion and to make true dynamic gait analysis of the patient's natural gait. In the known prior art, small platforms or the like are provided on which a patient walks or stands, and either a measurement, a print or another image is obtained of the foot at a particular instant of time only. Thus, in many of the prior art apparatus the results provide static measurement, merely measure or analyze one foot at a time without taking into consideration the effect the other foot has on the measured foot, or fails to show the effect on, for example, the heel of the foot when the toe is just coming off etc. Neither does any prior art quantify the length of time in various parts of the gait cycle in standardized normals, baselines or typical pathological patterns. Examples of such prior art are the Walking Program Record marketed by Shutrak.RTM. which provides foot prints on a carbonized sheet of paper (see U.S. Pat. No. 4,183,552) as a patient walks or stands on a hard surface, and the piezoelectric measuring platform marketed by Kistler which provides a static measurement of the force components on one foot along three axes. In Elftman U.S. Pat. No. 2,325,490, a patient walks over a light reflective material on a transparent plate to press the material against the plate for obtaining photographic recordings of the pressure areas. However, the foot per se is not visualized--only the points of pressure contact of the reflecting material and again no time relationships are derived. Moreover, the actual surface area of a foot is not obtained because of the "cone" effect due to the foot contacting the reflecting material. In Hagy et al. U.S. Pat. No. 3,894,437 and Manley et al. U.S. Pat. No. 4,267,728 a subject walks on a small force plate or transparent platform and the forces on one foot at a time of the subject is analyzed. The apparatus in both of these patents results in the subject unnaturally altering his gait so as to step with the one foot onto the platform. Moreover, only the force at a specific instant of time is determined. In Anderson et al. U.S. Pat. No. 4,416,293 a subject strides on a treadmill and the gait is observed by video and audio equipment. Here the upper body is fixed by holding rails of the treadmill so that the natural gait of the subject is again altered and the plantar aspect of the foot is not visualized.
An additional difficulty not addressed by or adequately solved by the prior art when viewing the foot when it is pressed against a hard surface, is the determination of the true beginning and termination of the contact area. Since the bottom of the foot is an uneven pliable compressible heated surface there is a problem with determining surface area contact due to the lack of contrast between the areas of contact and noncontact plus the production of condensation as the foot contacts the surface when viewed through a transparent smooth rigid surface at ambient temperature.